Method and apparatus for spraying metal



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March 5, 1957 GFELLER 2,784,029

METHOD AND APPARATUS FOR SPRAYING METAL Filed Feb. 16, 1954 a sheets-sheet 1 I NVENTOR 779/72 x v-44516 ATTORN Y6 March 5, 1957 METHOD AND APPARATUS FOR SPRAYING METAL Filed Feb. 16, 1954 s Sheets-Sheet 2 E f m h g Q m m W 3- 1 B R i v I \B :J/V/

m b N w m y Kg 1 Q 3 N 15 INVENTOR BY 5M Wm 4? ATTORN Y6 F. GFELLER 2,784,029

March 5, 1957 F. GFELLER 2,784,029

METHOD AND APPARATUS FOR SFRAYING METAL Filed Feb. 16, 1954 5 Shets-Sheet s INVENTOR 7 /9/72 GPA-245,?

2,784,029 METHOD AND APPARATUS ron SPRAYING METAL r r thereof. However, the end of the wire must emerge from v the guide sleeve into the combustion chamber at such a Fritz Gfeller, Zurich, Switzerland, assignor to Martin Von Schulthess & (30., Zurich, Switzerland, a Swiss company Application February 16, 1954, Serial No. 410,646

Claims priority, application Switzerland February 19, 1953 24 Claims. (Cl. 299-283) The invention relates to a process for producing. a homogeneous spray of metal in a gaseous envelope, and to an apparatus for carrying out this process.

In spraying processes heretofore known, the metals which are being sprayed come in contact with oxygen during the melting and atomizing phases and therefore may become oxidized. atomization of the molten metal generally results in a coarse-grained and non-homogeneous spray. The coating formed by such a spray absorbs corrosion-promoting liquids and also traps dirt in its pores. The spray coatings thus formed must, therefore, be subsequently treated with corrosion-resistant impregnating agents in order to render them more corrosion resistant.

The primary object of the present invention is to overcome these disadvantages of the known processes.

Another object of the invention is to expel the metals homogeneously in the exhaust spray from a combustion chamber filled with combustion gases.

According to the invention, the metal wire which is to be atomized, is positioned in a guide sleeve, in which it is pre-heated by rearwardly flowing combustion gases and.

through the chamber in any suitable fashion, it finally reaches the outlet where it is melted, atomized into a homogeneously fine suspension and then expelled into the open air. The atomization takes place while the molten metal is passing through the hottest zone of the stream of combustion gases.

The spray coating thus produced has a homogeneous texture composed of mutually sintered and partially molten droplets. By properly choosing the diameter of the metal wire to be atomized, its rate of advancement, the gas pressure and the cross-section of the outlet, the metal can be sprayed onto an object to form a layer of practically invisible grain size.

This procedure produces a spray in as large volume and at as high a rate as a workman is able to handle. It allows especially the low-melting metals, such as lead, zinc or tin, to be sprayed much more rapidly than heretofore.

A further object of the invention is to provide an apparatus for carrying out this process.

This apparatus of the invention includes a pressureresistant combustion chamber, having cooling means and ignition means, and provided with gas supply ducts. It also has an exhaust opening or combustion chamber outlet, and a longitudinally adjustably mounted wire guide sleeve which terminates in the interior of the combustion chamber opposite the exhaust. The wire guide sleeve can terminate at a point in the combustion chamber remote from the exhaust aperture or in the immediate vicinity In these processes, also, the.

point that the wire must travel a greater or less distance toward the exhaust opening, and be thus exposed to the combustion gases in the chamber.

The wire guide sleeve is of somewhat greater crosssection than the wire, so that hot combustion products from the chamber can flow back through the guide and preheat the wire therein.

The pressure and amount of combustion gases can be increased or reduced, so that the wire which enters the combustion chamber and is continually advanced therethrough will be preheated to near its melting point by the combined action of the heat within'the chamber and combustion gases flowing rearwardly through the guide sleeve.

The wire guide sleeve need not, under some conditions, extend into the combustion chamber at all. the wire moves freely across the space between the forward end of the wire guide sleeve and the outlet opening of the cone-shaped combustion chamber.

According to another feature of the invention, there' is provided a conical body extending into the combustion chamber through which the guide sleeve extends. The compressed air ductconnects with this conical member, and the compressed air in this duct completely envelopes and cools the outside of the guide sleeve. This prevents the melting end of the wire in the combustion chamber outlet or the unmolten but hot wire in the guide sleeve from combining or alloying with any part of the combustion chamber or the sleeve, and thus avoids the danger that the wire guide sleeve might be plugged up. In this particular embodiment the wire is at all times free to be advanced toward the nozzle.

In the combustion chamber the wire then enters into that zone where it is melted, atomized into a uniform mist and expelled into the open air without coming in contact with oxygen or atmospheric air. It is preferable tointroduce the combustion gases (that is, the fluid fuel and the oxygen containing gas, such as air) separately into the combustion chamber. The air necessary for the combustion may be pre-heated, if desired. The wire guide sleeve may be cooled with air or any other medium.

It is desirable that the combustion gases enter the combustion chamber at'uniformly distributed points and that they become completely mixed before they are ignited. This is accomplished by arranging the gas feed lines in an annular fashion around the wire guide sleeve, as in a shower head. The gas and air feed lines are paired off, and preferably terminate at right angles to each other, so that the streams of fuel gas and air intersect. This system of feed ducts is so arranged that the gas mixture thus formed immediately moves past a spark plug.

In the apparatus, the spark plug preferably has only one electrode and the spark discharges between this electrode and the body of the combustion chamber. The electrode is suitably recessed in a well or recess in the wall of the combustion chamber.

The combustion chamber has a semi-circular shape and comprises cooling fins of which at least some extend beyond the exhaust opening. In this way the combustion chamber will not be damaged by overheating even at high output rates. The combustion chamber may also be cooled in other ways. The use of cooling fins, how ever, presents a very simple structure.

The elements which guide the cooling air around the wire guide sleeve can be constructed so as to serve simultaneously as combustion nozzles or as gas distributing.

nozzles. Thefront element, which is exposed to the combustion gases, may comprise annularly disposed apertures for the gas and the air arranged in separate spaced rows. The gas apertures on the back side of this element may Patented Mar. 5, 1957- In that case,

be connected with each other by an annular channel. The gas can enter the annular channel through sieve-like aper tures in a rear guide element.

An apparatus in accordance with the invention is shown in the attached drawingsin the form of a hand-operated device. A plurality of such apparatus can be employed in groups mounted on stationary or movable supports, in a; fixed or an articulate position, either as fully or semiautomatic devices.

Further objects and advantages of the invention will appear more fully from the following description, especially when taken in conjunction with the accompanying drawings, which form a part thereof.

In the drawings:

-'Fig. 1 shows in side elevation an apparatus'in accordance with the invention, the lower portion of the combustionchamber being shown in section;

- "Fig. 2. is a front view of the apparatus;

Fig. 3 is a longitudinal vertical section through the head of the apparatus;

Fig. 4 is a longitudinal section through the combustion chamber of a modified form of the invention'at a dilterent angle from Fig. l; and

Fig- 5 is a schematic drawing explanatory of the ap paratus in accordance with the invention.

Figs. 1 and 2 show the apparatus in accordance with the invention without the wire advancing mechanism, which may be of conventional type. A cone-shaped base 1, made of light metal having a flange-like reinforcing portion 2' is bolted to a combustion chamber 3 in such a way that the combustion chamber encloses and covers a combustion nozzle 4. The threaded engaging means comprise four threaded bolts 5 each provided with a hexagonal internal recess for inserting a hexagonal key by which the bolts can be screwed into the combustion chamber, and nuts 6 with annular spring washers 7. These fastening means make it possible for the combustion chamber 3 to adapt itself to changes in shape caused by heat expansion without developing'any air leaks, principally because of the presence of spring washers 7.

' The base 1 has on its rearward end a coupling fitting 8 for the purpose of mounting and aligning the wire advancing mechanism. On the underside of base 1, between two of the bolt recesses, feed line 9 for the combustion air and feed line 10 for the combustion gas are threadedly engaged in the base. These feed lines 9 and 1t) form the skeleton of the handle. Feed line It) is threaded into valve housing 11 at its lower end, while feed line 9 is seated in an open channel of valve housing 11 and protrudes beyond the housing. The protruding end 12 is threaded for the purpose of receiving a hose fitting. Feed line 9 is rigidly connected to valve housing 11 by conical cotter key 13 and is held against rotation thereby when the hose fitting is threadedly engaged therewith. The housing 11 contains a valve 14 of known construction so that the operator can shut off the gas supply it there is danger of tire, or, if the flame in thecombu'stion chamber is accidentally extinguished, to prevent gas leakage and possible poisoning of the operator.

On the underside of valve housing 11 which is made of light metal, there is a steel plate 15 having a threaded fitting 1-6 welded thereon for the purpose of attaching a gas hose. Steel plate 15 has a flange 17 which extends rearwardly and serves to form the lower point of support for the wire advancing mechanism.

On the upper portion of feed lines 9 and 10. is a cross. piece 18 fixedly mounted thereon in such a manner that the thinner gas line 10 passes through it and the thicker air feed line 9 is seated in a semi-circular recess in the cross-piece. The cross-piece 18 and the air feed line are rigidly connected with each other by conical cotter key 19, so that they form a portion of the rigid skeleton for the handle. A V-shaped handle casing. 20 is slipped over the cross-piece 18 and the upper part of valve house ing 11 and this handle casing is fastened tocross-piece L8 and housing 11 by screws 21. The handle casing 20 is formed with a plurality of slits 22, which give the casing a comb-like structure. Casing 20 is held out of direct contact with feed line 10, so that the hand of the operator is protected from the heat in the event of a back-fire in line 10 caused by faulty operation of the spray gun, and also in order to give the operator a better grip on the handle. Cross-piece 18 also has a protective shield 24 mounted thereon by means of two screws 25, which protects the hand of the operator from the heat radiating from the hot combustion chamber 3.

Combustion chamber 3 is equipped with a spark plug 26 which is seated in a projecting socket or well 27. The usual copper-asbestos washer 28 is inserted between the spark plug and the socket. The spark plug 26 serves merely to initiate the combustion.

The spark plug 26 has only one electrode 26 so that the ignition spark discharges between the electrode and the body of the combustion chamber.

Combustion chamber 3 is provided with twenty-four cooling ribs 29 and 30. The six ribs 29 extend in a forward direction beyond the exhaust aperture 31 in order to protect the forward-most and most highly heated portion of the combustion chamber from excess heat.

Fig. 3 shows the head of the spray gun in detail. Light metal socket 1 has a longitudinal, centrally located bore 32 passing therethrough. Feed line 9 is threadedly engaged with threaded stud 33 and leads into bore 32. The forward portion of socket 1 has a flange-like enlargement 2 and is machined to form a cup-shaped recess at the bottom of which there is an annular depression 33'. A hole 34 extends rearwardly from the lower portion of the depression 33'. Fuel feed line 10 communicates with the hole 34 and is held in place by a threaded fitting. A gas distribution plate 35 is mounted gas-tight in the bottom of the cup-shaped recess and centered by projecting portion 36 seated in recess 32. This plate covers the annular channel 33 in socket 1, and is provided with apertures 37 which communicate with annular channel 33'. On its forward side the gas distribution plate 35 has a round projection 38 which fits into the base of and thus centers the combustion nozzle 4. A tubular portion 39 with a tapered end extends forward from the enlarged projection 38. A bore 40 extends through portion 39, and the center of the distribution plate 35, this bore forming an extension of bore 32 in socket 1.

Combustion nozzle 4 fits over tubular member 39 and is held in gas-tight engagement with distribution plate 35. The combustion nozzle 4 has a conical tubular portion 41 at its forward end. On the side facing socket 1 the combustion nozzle 4 is provided with an annular channel 42 which communicates with annular channel 33 through holes 37 in distribution plate 35. Combustion nozzle 4 also has a number of circumferentially equally distributed apertures 43 communicating with annular channel 42. These apertures are rearwardly flared to form cones, but their forward portions are cylindrical. Apertures 43 extend through the'entire thickness of nozale 4 and lead into combustion space R of chamber 3. Equally distributed around the entire circumference of the base of conical member 41 are radial bores 44 which connect combustion space R with the hollow space 45 between member 41 and tubular member 39.

Bore 32 in base 1 has a threaded portion 46 in its rear end. A wire guide sleeve 47 extends through bore 32 and its forward end is pointed and forms a gas-tight seal with an internal tapered seat at the apex of conical member 41. Wire guide sleeve 47 has a portion 48 of reduced diameter at its rearward end. A centering disc 49, a compression spring 50 and a second disc 51 are slipped over the portion48 of the wire guide sleeve so that, when bore 32 is closed by threaded member 52, the forward pointed end of the guide sleeve is resiliently seated in the conical portion of nozzle 4. For greater pressure, a washer 53 may be used in front of closure 52 I Thisres'ilient pressure exerted by wire guide sleeve 5 against conical member 4l causes the heat expansions of the two contacting elements to be compensated for.

A helical guide member 54 is loosely mounted in bore 32. Guide member 54 is formed from a metal rod having a rectangular cross-section, and forces the flow of entering compressed air from pipe 9, which connects with the rear end of recess 32, to assume a rotary motion about guide sleeve 47. Guide member 54 is held in place in bore 32 more or less loosely between centering stud 36 at one end and centering disc 49 at the other end.

The cooling and combustion air therefore enters through feed line 9 into bore 32, rotates around wire guide sleeve 47 guided by spiral member 54, then passes through bore 40, flows to the point of the wire guide sleeve 47, turns around and flows in the opposite direction-through the space 45 between parts 39 and 41, then into bores 44 and finally enters radially and in a showerlikefashion into combustion space R or combustion chamber 3. The combustion gas, however, enters through feed line into hole 34, from there into annular channel 33, through bores 37 into annular channel 42 and finally flows radially through bores 43 in a showerlike fashion into combustion space R of combustion chamber 3. Thus, the combustion gases and the air do not mix until they reach combustion space R. Their direction of flow at the entrance to space R is at right angles to each other, but gas jet bores 43 and air jet bores 44 are paired off in the same radial planes of combustion chamber 3, so that the two media must impinge upon each other and thus create common eddies, because of the different diameters of the bores 43 and 44 and the different rates of flow of the individual media.

The combustion chamber also comprises a flange 55 for receiving bolts 5, as already described.

A spacing ring 56 is clamped between combustion chamber 3 and nozzle 4. By exchanging spacing ring 56 for :a thicker or thinner ring, or by entirely omitting ring 56 the distance between combustion chamber 3 and socket 1 can be decreased or increased while the joint remains gas-tight, so that, as already described, the forward end of Wire guide sleeve 47 can be moved closer to or farther away from the exhaust opening 31.

Fig. 4 is a longitudinal section through combustion chamber 3', the combustion nozzle 4 and the distribution plate 35 in a plane at an angle of 22 30' from the plane of Fig. 3, and showing a modification. Parts corresponding to those of Figs. 1 to 3 bear the same reference characters with prime designations. The distribution plate 35, in addition to the structure shown in Fig. l, is also provided with radial passages 56 which are uniformly distributed over the entire circumference between bores 37. Passages 56 are connected with space 45 by axial bores 57 so that a part of the cooling and combustion air can escape into the atmosphere instead of flowing into combustion space R. In this way, the wire guide sleeve 47' the nozzle 4', and the distribution plate 35' are additionally cooled and the gas pres sure in space R is maintained resilient, so that fluctuations of the pressure in the combustion chamber are automatically compensated for. In this figure the exhaust opening 31 is enlarged and a separate nozzle fitting 58 is inserted. The nozzle fitting 53, of sintered metal, has a forwardly converging conical cross-section and is pressed against the correspondingly shaped seating surface by the operating pressure in combustion chamber 3'. Such a nozzle fitting can be changed whenever desired for one having the same or a different size or shape of exhaust opening. This figure also shows the spacing ring 56 completely omitted, so that the wire guide sleeve 47 extends as far forward into the combustion space R and as close to exhaust opening 31 as possible.

The schematic view of Fig. 5 with its graphic representationof the paths of fluid flow should be understandable without special commentary. 7

The wire guide 47 (or 47) is of somewhat larger internal cross-section than the wire 59, as is also the hole in closure 52, so that some of the combustion products can pass backward from the combustion chamber in heat exchange relation with the wire to preheat it before it enters the combustion chamber.

The individual hollow spaces and other elements can be altered without departing from the scope of the invention. The wire guide sleeve 47 may have any suitably shaped bore for receiving the wire to be atomized. The metal wire may be maintained in a glowing state throughout the length of the guide sleeve 47. I The wire guide sleeve 47 can be made of copper or even silver if low melting point metals such as lead, tin or zinc are to be sprayed with it. The combustion chamber'3 is preferably made of heat-resistant steel as may be the nozzle 4 with its conical portion 41. All of the other elements are subjected to heat only to an insignificant degree. The parts which are subjected tolarge heat differentials may also be made of heat-resistant alloys.

While I have described herein some embodiments of my invention, 1 wish it to be understood that I do not intend to limit myself thereby except within the scope of the claims hereto or hereinafter appended.

I claim:

1. A process for producing a homogeneous metal spray, which comprises advancing a metal wire from a relatively cold zone into an incandescent zone produced by an incandescent fuel mixture composed of a combustible fuel and an oxygen-containing gas, heating and atomizing said wire in said incandescent zone, and passing gaseous combustion products in heat-exchange relation with the wire in a direction opposite to the direction of advancement of the wire, to preheat the wire prior to its entrance into the incandescent zone.

2. A process for producing a homogeneous metal spray, which comprises advancing a metal wire from a relatively cold zone into an incandescent zone produced by an incandescent fuel mixture composed of a combustible fuel and an oxygen-containing gas, heating and atomizing said wire in said incandescent zone, passing gaseous combustion products from the combustion zone in heat-exchange relation with the wire in a direction opposite to the direction of advancement of the wire, to preheat the wire prior to its entrance into the incandescent zone, and simultaneously cooling said combustion products.

3. A process for producing a homogeneous metal spray, which comprises advancing a metal wire from a relatively cold zone into an incandescent zone produced by an incandescent fuel mixture composed of a coma bustible fuel and air, heating and atomizing said wire in said incandescent zone, passing gaseous combustion products from the combustion zone in heat-exchange re-' lation with the wire in a direction opposite to the direction of advancement of the wire, to preheat the wire prior to its entrance into the incandescent zone, and simultaneously cooling said combustion products with air.

4'. A process for producing a homogeneous metal spray, which comprises advancing a metal wire from a relatively cold zone into an incandescent zone produced by an incandescent fuel mixture composed of a combustible fuel and an oxygen-containing gas, melting and satomizing said wire in said incandescent zone, passing gaseous combustion products from said incandescent fuel mixture in heat-exchange relation with the wire in a di rection opposite to the direction of advancement of the wire to preheat the wire prior to its entrance into the incandescent zone, and passing relatively cold air first in heat-exchange relation with said combustion products tocool the same and then to the incandescent zone.

5, A process for producing a homogeneous metal spray, which comprises forming an incandescent zone by aton izing a liquid combustible fuel with a compressed oxygen-containing gas and igniting the resulting combus: tible fuel mixture, advancing a metal wire from a relatively cold zone into said incandescent zone, melting and atomizing said wire in said incandescent zone, and passing gaseous combustion products from said incandescent zone in heat-exchange relation with the wire in a direction opposite to the direction of the advancement of the wire to preheat the wire prior to its entrance into the in candescent zone, while simultaneously cooling said combustion products.

6. A process for producing a homogeneous metal spray, which comprises forming an incandescent zone by atomizing a combustible fuel in a shower-like pattern, bringing the how of atomized fuel into contact with a flow of an oxygen-containing gas at substantially right angles to each other, and igniting the resulting combustible fuel mixture, advancing a metal wire from a relatively cold zone into said incandescent zone, melting and atomizing said wire in said incandescent zone, and passig gaseous combustion products from said incandescent zone in heat-exchange relation with the wire in a direction opposite to the direction of the advancement of the wire to preheat the wire prior to its entrance into the incandescent zone, while simultaneously cooling said combustion products.

7. A process for producing a homogeneous metal spray, which comprises advancing a metal wire from a relatively cold zone into an incandescent zone produced by an incandescent fuel mixture composed of a combustible fuel and air, melting and atomizing said Wire in said incandescent zone, passing gaseous combustion products from said incandescent fuel mixture in heat-exchange relation with the wire in a direction opposite to the direction of advancement of the wire to preheat the wire prior to its entrance into the incandescent zone, and passing relatively cold air first in heat-exchange relation with said combustion products to cool the same, and then passing a portion of the cooling air to the incandescent zone While discarding the remaining portion.

8,. In an apparatus for spraying metal comprising a front end and a rearward end, means on said front end forming a combustion chamber having an outlet, a metal wire, means to guide said wire from said rearward end into said combustion chamber, said guide means including a sleeve of greater internal cross-section than the wire, said sleeve extending from the combustion chamber to the rearward end oi the apparatus, means to feed combustihis material to said combustion chamber and to burn it therein so as to heat and atomize the wire and to expel the atomized wire through said outlet, and a continuous substantially annular space between said sleeve and said wire along the entire length of said sleeve to pass gaseous combustion products rearwardly from said chamber to said rearward end and out into the atmosphere in heat exchange relation with the wire along the entire length of the wire located within said sleeve, the axis of said sleeve being directed toward saidoutlet, means to adjust the space between the end of the sleeve nearest said outlet and the outlet.

9. In an apparatus for spraying metal comprising a front end and a rearward end, means on said front end forming a combustion chamber having an outlet, a metal wire, means to guide said wire from said rearward end into said combustion chamber, said guide means including a sleeve of greater internal cross-section than the wire, said sleeve extending from the combustion chamber to the, rearward end of the apparatus, means to feed combustible material to said combustion chamber and to burn it therein so as to heat and atomize the wire and to expel the atomized Wire through said outlet, and a continuous substantially; annular space between said sleeve and said wire along the entire length of saidsleeye to.

wire, means to guide said wire from said rearward end into said combustion chamber, said guide means including a sleeve of greater internal cross-section than the wire, said sleeve extending from the combustion chamber to the rearward end of the apparatus, means to feed com bustible material to said combustion chamber and to burn it therein so as to heat and atomize the wire and to expel the atomized wire through said outlet, and a continuo-us substantially annular space between said sleeve and said wire along the entire length of said sleeve to pass gaseous combustion products rearwardly from said chamber to said rearward end and out into the atmosphere in heat exchange relation with the wire along the entire length of the wire located within said sleeve, means forming a space around a part of said sleeve, a. helical member in said space around said sleeve, an air passage, and means connecting one end of said space to said air passage and the other end to the combustion chamber.

11. In an apparatus for spraying metal comprising a front end and a rearward end, means on said front end forming a combustion chamber having an outlet, at metal wire, means to guide said wire from said rearward end into said combustion chamber, said guide means including a sleeve of greater internal cross-section than the wire, said sleeve extending from the combustion chamber to the rearward end of the apparatus, means to feed combustible material to said combustion chamber and to burn it therein so as to heat and atomize the wire and to expel the atomized wire through said outlet, and a continuous substantially annular space between said sleeve and said wire along the entire length of said sleeve to pass gaseous combustion products rearwardly from said chamber to said rearward end and out into the atmosphere in heat exchange relation with the wire along the entire length of the wire located within said sleeve, and means forming a space around a part of said sleeve, a helical member in said space around said sleeve, an air passage, and means connecting one end of said space to said air passage and the other end to the combustion chamber, the means connecting the space to the combustion chamber including a cylindrical member surrounding the sleeve and spaced therefrom.

12. In an apparatus for spraying metal comprising a front end and a rearward end, means on said front end forming a combustion chamber having an outlet, a metal wire, means to guide said wire from said rearward end into said combustion chamber, said guide means including a sleeve of greater internal cross-section than the wire, said sleeve extending from the combustion chamber to the rearward end of the apparatus, means to feed combustible material to said combustion chamber and to burn it therein so as to heat and atomize the wire and to expel the atomized wire through said outlet, and a continuous substantially annular space between said sleeve and said wire along the entire length of said sleeve to pass gaseous combustion products rearwardly from said chamber to said rearward end and out into the atmosphere in heat exchange relation with the wire along the entire length of the wire located within said sleeve, a fixed member projecting into the combustion chamber and having an internal conical bore opening into the combustion chamber, the wire guide means comprising a sleeve having a conical end seated in said bore.

13. In an apparatus for spraying metal comprising a forming a combustion chamber having an outlet, a metal wire, means to guide said wire from said rearward end into said combustion chamber, said guide'means including a sleeve of greater internal cross-section than the wire, said sleeve extending from the combustion chamber to the rearward end of tthe apparatus, means to feed combustible material to said combustion chamber and to burn it therein so as to heat and atomize the wire and to expel the atomized wire through said outlet, and a continuous subtantially annular space between said sleeve and said wire along the entire length of said sleeve to pass gaseous combustion products rearwardly from said chamber to said rearward end and out into the atmosphere in heat exchange relation with the wire along the entire length of the wire located within said sleeve, a fixed member projecting into the combustion chamber and having an internalconical bore opening into the combustion chamber, the wire guide means comprising a sleeve having a conical end seated in said bore, and means resiliently urging said sleeve toward the combustion chamber against the wall of said bore.

14. In an apparatus for spraying metal comprising a front end and a rearward end, means on said front end forming a combustion chamber having an outlet, a metal wire, means to guide said wire from said rearward end into said combustion chamber, said guide means including a sleeve of greater internal cross-section than the wire, said sleeve extending from the combustion chamber to the rearward end of the apparatus, means to feed combustible material to said combustion chamber and to burn it therein so as to heat and atomize the wire and to expel the atomized wire through said outlet, and a continuous substantially annular space between said sleeve and said wire along the entire length of said sleeve to pass gaseous combustion products rearwardly from said chamber to said rearward end and out into the atmosphere in heat exchange relation with the wire along the entire length of the wire located within said sleeve, means forming a space around a part of said sleeve, a-helical member in said space around said sleeve, an air passage, and means connecting one end of said space to said air passage and the other end to the combustion chamber, a fixed member projecting into the combustion chamber and having an internal conical bore opening into the combustion chamber, the wire guide means comprising a sleeve having a conical end seated in said bore, and means resiliently urging said sleeve toward the combustion chamber against the wall of said bore.

15. In an apparatus for spraying metal comprising a front end and a rearward end, means on said front end forming a combustion chamber having an outlet, a metal wire, means to guide said wire from said rearward end into said combustion chamber, said guide means including a sleeve of greater internal cross-section than the wire, said sleeve extending from the combustion chamber to the rearward end of the apparatus, means to feed combustible material to said combustion chamber and to burn it therein so as to heat and atomize the wire and to expel the atomized wire through said outlet, and a continuous substantially annular space between said sleeve and said Wire along the entire length of said sleeve to pass gaseous combustion products rearwardly from said chamber to said rearward end and out into the atmosphere in heat exchange relation with the wire along the entire length of the wire located within said sleeve, a fixed hollow conical member projecting into the combustion chamber, a cylindrical member extending into the conical member and spaced therefrom, said wire guide means comprising a sleeve extending through both said members, spaced from said cylindrical memher and seated in the conical member, an air passage, means connecting the end of the cylindrical member remote from the combustion chamber to the air passage,

$113 and outlets: in :the. base .of the conical member leading into the1combustionchamber. 16;. "In an apparatus for spraying metal comprising 'a front end and a rearward end, means on said front end forming a combustion chamber having an outlet, a metal wire, means to guide said wire from said rearward end into said combustion chamber, said guide means including a sleeve. of greater. internal cross-section than the wire, .said sleeve extending from the combustion chamber to the rearward end of the apparatus, means to feed combustible material to said combustion chamber and to, burn it therein so as to heat and atomize the wire and to expel the atomized wire through said outlet, and a continuous substantially annular space between said sleeve and said wire along the entire length of said sleeve to pass gaseous combustion products rearwardly from said chamber to said rearward end and out into the atmosphere in heat exchange relation with the wire along the entire length of the wire located within said sleeve,

a fixed hollow conical member projecting into the combustion chamber, a cylindrical member extending into the conical member and spaced therefrom, said wire guide means comprising a sleeve extending through both said members, spaced from said cylindrical member and seated in the conical member, an air passage, means connecting the end of the cylindrical member remote from the combustion chamber to the air passage, and outlets in the base of the conical member leading into the combustion chamber, said connecting means including means forming a space around a part of said sleeve,-

and a helical member in said space around said sleeve.-

17. Apparatus for spraying metal comprising means forming a combustion chamber having an outlet, means to guide a wire into said combustion chamber, means to feed combustible material to said combustion chamber and to'burn it therein so as to heat and atomize the wire and toexpel the atomized wire through said outlet, a fixed hollow conical member projecting into the combustion chamber, a cylindrical member extending into the conical member and spaced therefrom, said wire guide means comprising a sleeve extending through both said members, spaced from the cylindrical member and seated in the conical member, an air passage, means connecting the end of the cylindrical member remote from the combustion chamber to the air passage, and outlets in the base of the conicalmember into the combustion chamber.

l8. Apparatus for spraying metal comprising-means forming a combustion chamber having an outlet, means to guide a wire into said combustion chamber, means to feed combustible material to said combustion chamber and to burn it therein so as to heat and atomize the wire and to expel the atomized wire through said outlet, said wire guide means including a sleeve, means forming a space around a part of said sleeve, a helical member in said space around said sleeve, an air passage, and means connecting one end of said space to said air passage and the other end to the combustion chamber.

19. In a metal spraying apparatus of the type described, a combustion chamber having an outlet therefrom, a metal wire to be atomized and sprayed, a Wire guide sleeve for said metal wire extending into and substantially through said combustion chamber terminating adjacent the outlet of said combustion chamber and being surrounded by said combustion chamber, means located rearwardly of the forward end of said wire guide sleeve to introduce a combustible gaseous fuel into said combustion chamber,

and means located rearwardly of the forward end of said ems-pea 11 through said combustion chamber terminating adjacent the outlet of said combustion. chamber and being Sui--- rounded by said combustion chamber, means located rearwardly of the forward end of said wire guide sleeve to introduce a combustible gaseous fuel into said combustion chamber, means located rearwardly of the forward end of said wire guide sleeve to introduce an oxygen-containing gas into said combustion chamber whereby saidfuel may be burned in said combustion chamber rearwardly of the forward end of said wire guide sleeve, and a space between said wire and said wire guide sleeve through which hot combustion gases may pass rearwardly to preheat said wire. a

21. In a metal spraying apparatus of the type described,-

a combustion chamber having an outlet therefrom, a metal wire to be atomized and sprayed, a wire guide sleeve for said metal wire extending into and substantially through said combustion chamber terminating adjacent the outlet of said combustion chamber and being surrounded by said combustion chamber, means located rearwardly of the forward end of said wire guide sleeve to introduce a combustible gaseous fuel into said combustion chamber, means located rearwardly of the forward end of said wire guide sleeve to introduce an oxygen-containing gas into said combustion chamber whereby said fuel may be burned in said combustion chamber rearwardly of the forward end of said wire guide sleeve, a space between said wire and said wire guide sleeve through which hot combustion gases may pass rearwardly to preheat said wire, and meansto cause said oxygen-containing gas to flow around said wire guide sleeve and then rearwardly into said combustion chamber.

22. In a metal spraying apparatus of the type described,

a substantially spherical combustion chamber having an' outlet opening at the forward side thereof and an inlet opening at the rearward side thereof, a metal wire to be atomized and sprayed, a wire guide sleeve extending through said inlet opening and through said combustion chamber substantially to the outlet opening thereof, means for introducing a combustible gas into said combustion chamber around said wire guide sleeve and rearwardly of the forward end of said wire guide sleeve, and means to burn said combustible gas in said combustion chamber around said wire guide sleeve and rearwardly of the forward end of said wire guide sleeve. 2

23. in a metal spraying apparatus of the type described, a substantially spherical combustion chamber having an outlet opening at' me forward side thereof and an inlet opening at the rearward side thereof, a metal wire to be atomized and sprayed, a wire guide sleeve extending through said inlet opening and through said combustion chamber substantially to the outlet opening thereof, means for introducing a combustible gas into said combustion chamber around said wire guide sleeve and rearwardly of the forward end of. said wire guide sleeve, means to burn said combustible gas in said combustion chamber around said wire guide sleeve and rearwardly of the forward end of said wire guide sleeve, and means to conduct a portion of the combustion gases rearwardly through said wire guide sleeve between the wire and the walls of said wire guide sleeve.

24. In a metal spraying apparatus of the type described, a substantiallyspherical combustion chamber having an outlet opening at the forward side thereof and an inlet opening at the rearward side thereof, a metal wire to be atomized and sprayed, a wire guide sleeve extending through said inlet opening and through said combustion chamber substantially to the outlet opening thereof, means for introducing a combustible gas into said combustion chamber around said Wire guide sleeve and rearwardly of the forward end of said wire guide sleeve, means to burn said combustible gas in said combustion chamber around said wire guide sleeve and rearwardly of the forward end of said wire guide sleeve, means to conduct a portion of the combustion gases rearwardly through said wire guide sleeve between the wire and the walls of said wire guide sleeve, a tubular member surrounding said wire guide sleeve to conduct oxygen-containing gas around said wire guide sleeve to substantially the forward side of said combustion chamber, a conical member surrounding said tubular member to conduct said oxygen-containing gas rearwardly and passages in said conical member to introduce said oxygen-containing gas into said combustion chamber rearwardly of the forward end of said wire guide 5 eeve.

References Cited in the file of this patent UNITED STATES PATENTS 2,092,150 Bleakley a Sept. ,7, 1937 2,108,998 Schori Feb. 22, 1938 2,268,202 Britton Dec. 30, 1941 2,551,114 Goddard May 1, 1951 

